Push-to-talk (PTT) generally refers to real-time direct one-to-one and one-to-group voice communication service, which may occur in the cellular, Public Switch Telephone Networks (PSTN) and Internet networks. PTT calls can be directed to both individuals and talk groups. In a PTT call, the call connection is initiated by an originator device while the receiver typically does not have to “answer” the call.
PTT calls are one-way communications (half-duplex), which means that while one person speaks the others listen. In a PTT conversation, users typically no longer need to make several calls to coordinate with a group.
PTT service users are typically engaged in some other activity than a telephone call, and they listen to the group traffic during their activity. A user is usually contacted by receiving a PTT call from a member of the PTT group and can respond to the PTT group with a push of a key.
Session Initiation Protocol (SIP) is a protocol which is based on a request-response model. SIP leaves open the particular implementation of the desired functionality, and for example does not provide for specific implementation of PTT. As the interpretation remains open, some implementations of PTT using SIP may lead to inefficiencies.
For example, in some conventional systems implementing PTT using SIP, media parameters are negotiated and communicated only once the PTT call is initiated by a user. This wastes resources and time between when the user actually initiates the PTT call and when the system connects the user to the receiving units. Call lags may occur each time a user initiates a PTT call. Further, such inefficiencies become magnified when the PTT group involves a large number of parties.
Other difficulties with existing conventional systems will be apparent to those skilled in the art in view of the detailed description below.
Similar reference numerals may have been used in different figures to denote similar components.